Operating a vehicle (e.g., a car, a truck, or a bike) is a challenging task because a driver has to learn to operate the vehicle, navigate within the limitations of traffic laws and the physical environment, and communicate with other proximate drivers in that same physical environment (e.g., a road, a parking lot, etc.). Regarding the last requirement, human drivers signal their intentions through a number of intentional and subconscious acts. Some of these signals rely on devices, which are purposely built into the vehicle, such as turn signals and brake lights. Other signals rely on innate human characteristics. These characteristics include intentional actions, such as waving a hand to signal another driver to proceed through an intersection and subconscious or reactive actions, such as a driver turning his head before merging lanes. When all other forms of signaling have failed, human drivers are usually able to speak their intentions or ask for assistance, such as when a vehicle breaks down or when a driver becomes lost.
The signals conveyed are perceived by external observers, such as pedestrians, other drivers, or traffic control officers. The external observers are able to interpret these signals to gain insight into a driver's intentions. These insights are important to enable safe and efficient flow of vehicular traffic as well as for providing assistance when needed. A central feature of ail of these methods is that an external observer need not employ any special equipment to understand the signal conveyed and most signals do not require any training to discern.
Advances in autonomous vehicles enable computers or other electronic devices to drive vehicles. At least two types of autonomous vehicles exist today—fully autonomous vehicles with no human passengers and semi-autonomous vehicles that are capable of operating in an autonomous mode while carrying human passengers. As the number of autonomous vehicles increases, there will be a need for better communication methods between the autonomous vehicles and external observers. Unfortunately, the signaling methods that are currently built into vehicles, such as turn signals and brake lights, only provide the ability to communicate a small subset of the information which is required. The signal and brake lights provide a limited ability to communicate with external observers. No known current autonomous vehicle provides a comprehensive means for signaling external observers.